• [FreeBSD-Announce] FreeBSD Security Advisory FreeBSD-SA-19:10.ufs

    From FreeBSD Security Advisories@21:1/5 to All on Tue Aug 13 05:48:33 2019
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    ============================================================================= FreeBSD-SA-19:10.ufs Security Advisory
    The FreeBSD Project

    Topic: Kernel stack disclosure in UFS/FFS

    Category: core
    Module: Kernel
    Announced: 2019-07-02
    Credits: David G. Lawrence <dg@dglawrence.com>
    Affects: All supported versions of FreeBSD.
    Corrected: 2019-05-10 23:45:16 UTC (stable/12, 12.0-STABLE)
    2019-07-02 00:02:16 UTC (releng/12.0, 12.0-RELEASE-p7)
    2019-05-10 23:46:42 UTC (stable/11, 11.2-STABLE)
    2019-07-02 00:02:16 UTC (releng/11.2, 11.2-RELEASE-p11)
    CVE Name: CVE-2019-5601

    For general information regarding FreeBSD Security Advisories,
    including descriptions of the fields above, security branches, and the following sections, please visit <URL:https://security.FreeBSD.org/>.

    I. Background

    The Berkeley Fast File System (FFS) is an implementation of the UNIX File System (UFS) filesystem used by FreeBSD.

    II. Problem Description

    A bug causes up to three bytes of kernel stack memory to be written to disk
    as uninitialized directory entry padding. This data can be viewed by any
    user with read access to the directory. Additionally, a malicious user with write access to a directory can cause up to 254 bytes of kernel stack memory
    to be exposed.

    III. Impact

    Some amount of the kernel stack is disclosed and written out to the
    filesystem.

    IV. Workaround

    No workaround is available but systems not using UFS/FFS are not affected.

    V. Solution

    Special note: This update also adds the -z flag to fsck_ffs to have it scrub the leaked information in the name padding of existing directories. It only needs to be run once on each UFS/FFS filesystem after a patched kernel is installed and running.

    Upgrade your vulnerable system to a supported FreeBSD stable or release / security branch (releng) dated after the correction date.

    Perform one of the following:

    1) To update your vulnerable system via a binary patch:

    Systems running a RELEASE version of FreeBSD on the i386 or amd64
    platforms can be updated via the freebsd-update(8) utility:

    # freebsd-update fetch
    # freebsd-update install

    Afterwards, reboot the system and run:

    # fsck -t ufs -f -p -T ufs:-z

    to clean up your existing filesystems.

    2) To update your vulnerable system via a source code patch:

    The following patches have been verified to apply to the applicable
    FreeBSD release branches.

    a) Download the relevant patch from the location below, and verify the
    detached PGP signature using your PGP utility.

    [FreeBSD 12.x]
    # fetch https://security.FreeBSD.org/patches/SA-19:10/ufs.12.patch
    # fetch https://security.FreeBSD.org/patches/SA-19:10/ufs.12.patch.asc
    # gpg --verify ufs.12.patch.asc

    [FreeBSD 11.x]
    # fetch https://security.FreeBSD.org/patches/SA-19:10/ufs.11.patch
    # fetch https://security.FreeBSD.org/patches/SA-19:10/ufs.11.patch.asc
    # gpg --verify ufs.11.patch.asc

    b) Apply the patch. Execute the following commands as root:

    # cd /usr/src
    # patch < /path/to/patch

    c) Recompile your kernel as described in <URL:https://www.FreeBSD.org/handbook/kernelconfig.html> and reboot the
    system and run:

    # fsck -t ufs -f -p -T ufs:-z

    to clean up your existing filesystems.

    VI. Correction details

    The following list contains the correction revision numbers for each
    affected branch.

    Branch/path Revision
    - ------------------------------------------------------------------------- stable/12/ r347474 releng/12.0/ r349623 stable/11/ r347475 releng/11.2/ r349623
    - -------------------------------------------------------------------------

    Note: This patch was applied to the stable/11 branch before the branch point for releng/11.3. As such, no patch is needed for any 11.3-BETA or -RC.

    To see which files were modified by a particular revision, run the
    following command, replacing NNNNNN with the revision number, on a
    machine with Subversion installed:

    # svn diff -cNNNNNN --summarize svn://svn.freebsd.org/base

    Or visit the following URL, replacing NNNNNN with the revision number:

    <URL:https://svnweb.freebsd.org/base?view=revision&revision=NNNNNN>

    VII. References

    <URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2019-5601>

    The latest revision of this advisory is available at <URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-19:10.ufs.asc> -----BEGIN PGP SIGNATURE-----

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